MulteFire (MF) is a wireless access technology for extending a Long Term Evolution (LTE) system to an unlicensed frequency band, and it is able to use this technology individually in an unlicensed spectrum without the aid of carriers at a licensed frequency band. In order to enable the other devices operated at the unlicensed frequency band (e.g., a Wireless Fidelity (WiFi) device) to fairly occupy a channel at the unlicensed frequency band and prevent these devices from interference with each other, a Listen Before Table (LBT) mechanism, similar to a WiFi carrier monitoring technology, has been introduced into an MF physical layer. In the case that the channel at the unlicensed frequency band has been occupied, i.e., the LBT mechanism is failed, a base station or a User Equipment (UE) may stop to transmit a signal. The base station or UE may transmit the signal only in the case that the channel is in an idle state, i.e., the LBT mechanism is succeeded.
In order to improve the transmission efficiency of a downlink common control signal from the base station under the LBT mechanism, a Discovery Reference Signal (DRS) has been introduced into MulteFire. The DRS contains the principal downlink common control signals, including system broadcast, Primary Synchronization Signal (PSS), Secondary Synchronization Signal (SSS), enhanced Primary Synchronization Signal (ePSS), enhanced Secondary Synchronization Signal (eSSS), Cell Reference Signal (CRS), Master Information Block (MIB), and System Information Block MulteFire (SIB-MF). Twelve or fourteen symbols within a downlink subframe are occupied by the DRS.
The UE may receive the DRS within a Discovery Signals Measurement Timing Configuration (DMTC) window, so as to perform downlink synchronization, and receive the MIB and SIB-MF. An MF cell may merely transmit the CSR within a DRS subframe or any other subframe where a Physical Downlink Shared Channel (PDSCH) is transmitted. Hence, the UE may merely perform channel measurement on an MF serving cell or an MF neighboring cell within the DMTC window, so as to perform cell selection, cell reselection or cell handover.
In the related art, in the case of transmitting DMTC information about the MF neighboring cells, the base station may merely transmit the DMTC information about the MF neighboring cells synchronized with the base station, or the DMTC information about the MF neighboring cells asynchronized with the base station. In the case that the UE needs to measure channel quality of the synchronized neighboring cells and the asynchronized neighboring cells, it is impossible for the UE to acquire the DMTC information about the synchronized neighboring cells and the asynchronized neighboring cells simultaneously, and at this time, the service transmission may be adversely affected.